1. ProjectIEEE 802.16 Broadband Wireless Access Working Group http://ieee802.org/16 TitleProposed E-MBS Channel Structure for 802.16m Date Submitted2008-9-5 Source(s)Shigeo Terabe, Tsuguhide Aoki Toshiba Corporation Yong Sun, Toshiba Research Europe Limited Voice: +81-428-344266 E-mail: shigeo.terabe@toshiba.co.jp Voice : +44-117-9060749 E-mail : Sun@toshiba-trel.com Re:Call for Contribution on Project 802.16m System Description Document (SDD) issued on 2008-07-29 (IEEE 802.16m-08/003r4) Topic covered: PHY aspects of E-MBS AbstractThis contribution proposes to apply ‘group-wise scrambling’ for E-MBS channel structure. It allows FDM allocation between unicast and E-MBS channel and significantly improves MBS spectral efficiency. PurposeFor discussion and approval by TGm NoticeThis document does not represent the agreed views of the IEEE 802.16 Working Group or any of its subgroups. It represents only the views of the participants listed in the “Source(s)” field above. It is offered as a basis for discussion. It is not binding on the contributor(s), who reserve(s) the right to add, amend or withdraw material contained herein. ReleaseThe contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.16. Patent Policy The contributor is familiar with the IEEE-SA Patent Policy and Procedures: andhttp://standards.ieee.org/guides/bylaws/sect6-7.html#6.http://standards.ieee.org/guides/opman/sect6.html#6.3 Further information is located at andhttp://standards.ieee.org/board/pat/pat-material.html.http://standards.ieee.org/board/pat

2. Introduction In IEEE 802.16m system requirement document (SRD), it was agreed that the higher spectral efficiency is required in 16m E-MBS at MBSFN deployment. In this contribution, we propose to apply a ‘group-wise scrambling’ technique into 16m E- MBS channel structure to improve MBS spectral efficiency. There are two significant improvements in MBS spectral efficiency. –FDM between unicast and MBS resource becomes applicable without any additional pilot overhead. This makes power boosting of MBS data transmission possible using a margin of the BS transmit power of unicast data transmission. –Sub-carrier groups have the de-correlated channel response so that additional diversity gain is obtained.

3. Conventional MBS Structure Each BS transmit the same pilot and data signal. MSs receive MBS signal with RF combining from each BS.

4. Proposed Group-wise scrambling process Split sub-carriers into several sub-carrier groups. –Each sub-carrier group contains at least one pilot symbol. Scramble MBS data in each group with the same BS-specific code as pilot symbol. Cell-1 Cell-2 Cell-n Group-wise Scrambling Same as the BS-specific code used for pilot Cell-n

5. Effects of proposed GS Low correlation between sub-carrier group Additional diversity gain Pilot symbols can be used by both unicast and MBS for channel estimation Possible cross-cast of MBS and unicast in sub-carrier level

6. Channel estimation for GS transmitted / received pilot signal transmitted / received MBS data signal Pilot signal only within sub-carrier group is used. Sum of the weighted channel response is common in each sub-carrier group. –Channel estimation is employed within sub-carrier group.

7. Sub-carrier group partition We define the sub-carrier groups as described below (assuming PUSC allocation). Two pilot symbols within sub-carrier group is multiplied by the same scrambling code. These pilot symbols in the same group can be used to improve the channel estimation performance.

8. Advantage of GS (1) - MBS boosting - Applying GS, unicast pilot can be used as MBS pilot in common so that sub- carrier based cross-cast becomes possible. The margin for unicast transmission power can be used for MBS transmission as illustrated right side of figure.

9. Advantage of GS (2) - Diversity effect - Table. Simulation condition Inter-site distance500m System bandwidth5MHz Number of MBS symbols 6 OFDM symbol Data modulation16QAM Channel codingTurbo code (K=4, R=1/2) Max-Log-Map (8 iteration) Channel estimationIdeal Path modelPedestrian B UE speed3km/h(fD=5.55Hz) Fig. MS location We assumed that MS is located at the BS-boundary with a geometry value of 95%. At that location, the r.m.s delay spread becomes almost the worst condition from the viewpoint of the delay spread. Diversity gain due to GS, relative to conventional MBS structure, is approximately 1.1dB at 1% BLER.

10. Summary We proposed to apply a group-wise scrambling technique into 16m E-MBS to improve MBS spectral efficiency. We showed two significant improvements in MBS spectral efficiency obtained from this technique. –MBS Boosting –Additional diversity gain

11. Proposed text in SDD 15. Support for Enhanced Multicast Broadcast Service 15.x E-MBS channel structure To improve MBS spectral efficiency, a group-wise scrambling is to be considered. The group-wise scrambling implies pre-coding method for the MBS data. The process includes: (1) All the MBS data sub-carriers are split into the sub-carrier groups with at least one pilot symbol. (2) All the MBS data symbols in each sub-carrier group are rotated by the same amount of phase as that of pilot symbol. Consequently, the relative phase differences from the pilot symbol to the MBS data symbols become the same. Since the signals within the sub-carrier group from each BS become the same, it is possible to realize the RF combining macro-diversity in the same manner as the BS-common pilot case. Fig. x. E-MBS channel structure with group-wise scrambling